Electrostatic precipitator equipment



y 7, 1940-v R. L. HILDEBRAND 2,200,085

ELECTROSTATIC PRECIPITATOR EQUIPMENT Filed April 15, 1938 To Alarm 0r Belay WITNESSES: 4 INVENTOR Ralph LHz'ldebrand.

0/ 40. T WM.

ATTORNEY Patented May 7, 1940 nnsc'raos'ra'rro ranorrrrsroa EQUIPMENT Ralph L. Hildebrand, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 15, 1938, Serial No. 202,232

12 Claims.

My invention relates to a reliable indicating and alarm system for use in connection with electrostatic gas-cleaning devices.

While my invention is generally applicable to :i electrostatic gas-cleaning devices of any type, it

has been more specifically adapted as an improvement over the invention which constitutes the subject matter of Gaylord W. Penneys application Serial No. 45,070, filed October 15, 1935, i Patent No. 2,129,783, granted September 13, 1938,

relating to a gas-purifying precipitator in which the gas is blown first through an ionizing chamber, and then through a separate precipitating chamber, a significant feature of the precipitator being that the ionizing wire is of such small diameter that practically utilizable ionization of suspended particles in the gas may be obtained at a wire-charging voltage which is below the critical corona voltage, so that the wire-charging voltage may be below this critical value, thereby limiting the ionizing current input and also limiting the ozone-generation when the precipitator is used for cleaning air.

Such a precipitator utilizes an ionizing wire of less than 32 mils thickness, which is a somewhat roughly critical value of the wire-diameter, somewhere near the knee of the curve expressing the relation between the critical corona voltage and the wire-diameter. In ordinary practice, the wire is much finer than this upper limit, and is frequently a tungsten wire 5 mils in diameter, or even very much less in diameter. As the result of the use of such fine wires, the current-input into the ionizing chamber is kept down to J very small values, of an order similar to the current-input into the precipitating chamber, so that it becomes possible to energize both chambers by means of a high-voltage rectifying powerunit having an extremely small current-rating, as distinguished from the very much larger currents which were fed into previous precipitating systems utilizing much heavier ionizing wires.

In the aforesaid Penney application, a special power-unit of limited energy-output was shown, 45 for applying unidirectional voltages to the ionizing wires and to the precipitating electrodes of an electrostatic precipitator, and particularly a fine-wire electrostatic Drecipitator of the type just described. Such a power-unit makes it possible for low-current tubes of small size to be utilized to rectify the high voltage which is ob tained by means of a step-up transformer, because an electrostatic precipitator has the habit of producing a momentary spark or flash, at infrequent intervals, as a result of a piece of lint or other dirt which might momentarily shortcircuit the equipment, so that it was necessary to limit the energy which would be withdrawn through the small rectifier-tubes during such flashes. As the equipment gets dirtier and dirtier, from the accumulation of foreign particles withdrawn from the gas being treated, these flashovers become more numerous and more severe. The equipment should be taken out of service long enough to flush it out with a water hose, or to otherwise clean it, before these flashover conditions get too severe, or lead even to failure or an inoperative condition, but it has been deemed necessary to provide some sort of means for indicating a failure or inoperative condition of the equipment, either because of a permanent shortcircuit, or because of breakage of the fine wire, or because of a failure of one of the rectifiertubes or other parts of the apparatus.

It is the particular object of my invention to provide a reliable indicating and alarm system for either showing the existence of any sort of failure of the apparatus, or, if desired, for shutting down the entire apparatus or any part of the entire apparatus.

In the original line-wire precipitator equipment, as shown in the aforesaid Penney application, failure was indicated by insulatedly mounting one of the low-tension tubular electrodes of the ionizing unit, and grounding this tubular electrode through a glow-tube or lamp which would go out when the ionizing input was reduced below a predetermined value. As the ionizing input into one of these tubular electrodes is but a small fraction of a milliampere, it will be obvious that the use of such a glow lamp was about all that could be undertaken.

In subsequent equipments, however, the urgent need for a better protective system than the glow lamp led to the utilization of insulating supports for a plurality of the tubes of the ionizing units, and connecting these insulated tubes to the precipitator-cabinet (or ground) through a very sensitive relay, which is capable of operating on a milliampere or less. This equipment adds considerable to the cost and complication of the ionizing unit, in requiring the use of insulators for supporting the tubular electrodes of the ionizing chamber, and the protective response itors are in the path of the dirty air stream, it will readily be perceived that the accumulation of dirt thereon constitutes quite a serious limitation upon the utility of such a device. This apparatus had the further disadvantage that, in the event of the breakage of one of the fine wires, causing the wire to lie across one of the insulated tubular electrodes, the ionizing voltage (of the order Of 12,000 volts) would be applied to the alarm circuit, which is highly dangerous.

According to my invention, the foregoing and other difliculties are avoided by the utilization of a special step-up transformer in the limitedenergy power-unit, and by the utilization of a special system of relays or voltage-responsive devices, in connection therewith, as will be subsequently explained more in detail.

With the foregoing objects in view, and others which will become apparent as the description proceeds, my invention consists in the systems, methods, apparatus and combinations hereinafter described and claimed, and illustrated in the accompanying drawing, the single figure of which is a diagrammatic view of circuits and apparatus illustrating my invention in a pre ferred form.

In the illustrated embodiment of my invention, which is only one of many forms which the in vention can take,air to be treated is drawn in through the bottom of a precipitator-cabinet as by means of a fan or blower 2. The air passes upwardly, first through an ionizing chamber 3, and then through a precipitating chamber 4, from the top of which the air is discharged from the apparatus.

The ionizing chamber usually comprises a plurality of ionizing units disposed transversely with respect to the direction of air flow, but for simplicity of illustration, only one of these ionizing units is illustrated in the drawing, and that illustration is somewhat schematic. In this ionizing unit, the air passes upwardly between two spaced horizontal tubular electrodes 5 which are grounded on the metal cabinet Between these two tubular electrodes there is suspended a fine ionizing wire 6 of the type which has already been discussed.

The precipitating chamber usually comprises a relatively large number of alternately insulated and non-insulated plates 1 and 8, these plates standing vertically, or parallel to the direction of air-flow. The insulated plates 1 are supported on notched bars 9 which are carried by insulators l0, while the non-insulated plates 8 are carried by notched bars |2 which are grounded on the metal cabinet Electrical energy is supplied to this precipitator-apparatus by means of a power-unit which derives its energy from a l10v'olt alternatingcurrent line H, or any other suitable source of alternating-current supply.The power-unit comprises a specially designed step-up transformer l5 having a magnetizable circuit including a primary portion IS, a secondary portion l1, and a magnetic-leakage path l8 therebetween, the magnetic-leakage path preferably including an air-gap l9 or its equivalent. On the primary portion H; of the magnetizable circuit, this transformer carries a low-voltage primary winding 2| and two separately insulated filament-circuit auxiliary windings 22 and 23 which are usually of considerably lower voltage. On the secondary portion I! of the magnetizable circuit, this transformer carries a high-voltage secondary winding 24 which, in the illustrated embodiment of the invention, is provided with an intermediate tap 26 near one end. This secondary portion ll of the magnetizable circuit also carries a low-voltage tertiary winding 26.

Energy is derived from the secondary winding 24 and applied to the ionizing wire 6 and to the insulated precipitator-structure 9 in any convenient manner, the illustrated embodiment being the same as that which is shown in the Penney application, and involving two rectifier-tubes 3| and 32 having filamentary cathodes which are energized from the auxiliary transformer-windings 22 and 23, respectively, these rectifier-tubes being utilized to cumulatively charge two serially connected capacitors 33 and 34, the charges on which are indicated by plus and minus signs. The negative terminal of the capacitor 34 is grounded on the cabinet I. The positive terminal of this capacitor is connected, at 36, to the insulated precipitating structure |--9. The negative terminal of the capacitor 33 is connected to the same point 36, while the positive terminal of this capacitor 33 is connected, at 31, to the ionizing wire or wires 6. As a result of the foregoing construction, it is possible to apply a volt-- age of the order of 5,000 volts to the oppositely charged precipitating electrodes I and 8, and a voltage of the order of 12,000 volts to the ionizing wire 6.

My protective equipment is energized from the tertiary transformer-winding 26, and it comprises essentially an under-voltage relay 4| and an over-voltage relay 42, both relays being energized from the tertiary winding 26.

Under normal operating conditions, enough voltage is applied to the under-voltage relay 4| to cause it to keep its back-contacts 43 open, so that this relay will respond to an abnormal drop in voltage by closing its contacts 43. The voltage existing under normal conditions is not sufficient, however, to fully energize the over-voltage relay 42, so that its front or make" contacts 44 are normally open under these conditions, but

this relay will respond to an abnormal increase in voltage to close its contacts 44. An alarm or relaying circuit 45 is energized, in response to a response of either one of the relays 4| or 42, that is, whenever either one of the contact members 43 and 44 is closed, this relay or alarm circuit 45 being illustrated as being energized from 110- volt line 4.

In operation, it will be observed that the voltage of the tertiary winding 26 will always be proportional to the voltage of the secondary winding 24, because both windings are interlinked with the same portion ll of the magnetizable circuit of the transformer l5, with relatively little leakage between the two windings. A separately insulated tertiary winding 26 is utilized, rather than taps on the secondary winding 24, because this secondary winding, as a whole, may rise to 8,000 to 14,000 volts above ground, particularly in the illustrated form of embodiment.

My protective equipment operates as follows, Any faulty operation of the entire equipment will manifest itself in the power-supply, by changing the load on the transformer secondary winding 24, and since the transformer I5 is provided with the magnetic-leakage path l8, so as to give the transformer a poor voltage-regulation, the secondary voltage varies strongly with slight changes in the secondary load, and, of course, the tertiary voltage of the relaying winding 26 follows the secondary voltage, as already expiained. If one of the rectifying tubes II and 32 should fail, or if one of the fine ionizing wires 8 should break, the usual result is to decrease the load on the secondary winding, hence increasing the relaying voltage supplied by the.

tertiary winding 26 to the over-voltage relay 42, and causing the latter to respond by picking up and closing its make" contacts 44. Foreign material on or between the precipitating plates 1 and 8, causing short-circuits, and short-circuits produced from any other cause, will usually increase the secondary load, thereby decreasing the relaying voltage applied to the uncle -voltage relay 4 l, causing the same to respond by dropping out and closing its back-contacts 43. These changes in the relaying voltage are really very positive indications of any abnormality in the equipment, because of the very poor voltageregulation of the transformer i5, causing the voltage of the tertiary winding 26 to respond very sensitively to even slight changes in the secondary load.

One or both of the relays ll and 42 may be provided with any suitable time-delay mechanism, as indicated symbolically by the dashpot 4B, which is illustrated as being associated with the under-voltage relay II, as it is more important that the action of this relay should be retarded so that the relay will not respond to momentary cracklings or flashes which last but an instant and clear themselves without doing any harm at all, as when a piece of lint gets across two of the oppositely charged precipitator-plates 1 and 8.

As illustrated in the drawing, a voltmeter 47 may also be energized across the tertiary transformer-winding 26, and its scale 48 may be marked to indicate a normal voltage-range in the center, and abnormal values of voltages at either extreme of the scale.

In the foregoing description and in the appended claims, when I refer to the critical corona voltage of the ionizing wire, I refer to the lowest voltage which produces a corona-discharge of the sort which is visible in sunlight, which is the kind of corona which was obtained in electrostatic precipitating equipments prior to Mr. Penneys introduction of the critically' fine ionizing wire. With the hereinabove described fine ionizing wire, the ionizing voltage which it is necessary to utilize, in order to obtain a substantially utilizable degree of ionization of the suspended particles in the gas being treated, is very much below this critical corona voltage, so that there is no corona-discharge which is visible in sunlight. In a dark room, however, there will be a corona-glow which is distinctly visible, surrounding the ionizing wire 5 as a result of the very slight discharge therefrom.

While I have described my invention in a preferred form of embodiment, and have suggested certain limitations in accordance with my best understanding of the same at the present time, I desire it to be distinctly understood that I am not altogether limited to these limitations or understandings, or to the particular form of embodiment shown in the drawing. I desire, therefore, that the appended claims shall be accorded the broadest constructions consistent with their language and the prior art.

I claim as my invention:

1. A gas-purifying precipitator-assembly comprising electrostatic gas-cleaning means for ionizing foreign particles in the gas and for electrostatically attracting said ionized particles; limited-energy, voltage-conversion, relatively highvoltage means comprising a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said stepup transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit, and means associated with said secondary winding for energizing said gascleaninr means; and an unoervoltage relay and an overvoltage relay both energized from said tertiary winding, said relays making a predetermined response or responses to an abnormal drop in voltage and an abnormal increase in voltage, respectively, and circuit-means responsive to a response of either of said relays.

2. A gas-purifying precipitator-assembly comprising an ionizing chamber, a separate precipitating chamber, and means for causing a gas-flow successively through first said ionizing chamber and then said precipitating chamber, said ionizing chamber comprising one or more insulatedly supported fine wires spaced between substantially uninsulated large electrodes; said precipitating chamber comprising oppositely charged, spaced precipitating electrodes substantially parallel to the direction of gas-flow; a stepup transformer having a magnetizable circuit including a primary portion, a secondary por tion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable'circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages both to said ionizing wire or wires and to said precipitating electrodes; said ionizing wire or wires being of less than 32 mils diameter and being of such fineness that substantially utilizable ionization of suspended particles in the gas is obtained at a low ionizing current with a wire-charging voltage below the critical corona voltage, the unidirectional wire-charging voltage being below said critical corona voltage; and an undervoltage relay and an overvoltage relay both energized from said tertiary winding. said relays making a predetermined response or responses to an abnormal drop in voltage and an abnormal increase in voltage, respectively, and circuit-means responsive to a response of either of said relays.

3. A gas-purifying precipitator-assembly comprising electrostatic gas-cleaning means for ionizing foreign particles in the gas and for electrostatically attracting said ionized particles; limited-energy, voltage-conversion, relatively high-voltage means comprising a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said stepup transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit. and means associated with said secondary winding for energizing said gascleaning means; and means energized from said tertiary winding for obtaining a predetermined response or responses both when the voltage increases and when the voltage decreases withrespect to a predetermined range.

4. A gas-purifying precipitator-assembly comprising an ionizing chamber, a separate precipitating chamber, and means for causing a gasiiow successively through first said ionizing chamber and then said precipitating chamber, said ionizing chamber comprising one or more insulatedly supported flne wires spaced between substantiallyuninsulated large electrodes; said precipitating chamber comprising oppositely charged, spaced precipitating electrodes substantially parallel to the direction of gas-flow; a stepup transformer having a magnetizable'circult including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages both to said ionizing wire or wires and to said precipitating electrodes; said ionizing wire or wires being of less than 32 mils diameter and being of such fineness that substantially utilizable ionization of suspended particles in the gas is obtained at a low ionizing current with a wirecharging voltage below the critical corona vo1tage, the unidirectional Wire-charging voltage being below said critical corona voltage; and means energized from said tertiary winding for obtaining a predetermined response or responses both when the voltage increases and when the voltage decreases with respect to a predetermined range.

5. A gas-purifying precipitator-assembly comprising electrostatic gas-cleaning means for ionizing foreign particles in the gas and for electrostatically attracting said ionized particles; limited-energy, voltage-conversion, relatively high-voltage means comprising a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said stepup transformer having a high-voltage secondary Winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit, and means associated with said secondary winding for energizing said gascleaning means; and means energized from said tertiary winding for obtaining a predetermined response or responses to voltage-decreases enduring for longer than a predetermined time such that there will not be a response to momentary flashes in the apparatus.

6. A gas-purifying precipitator-assembly comprising an ionizing chamber, a separate precipitating chamber, and means for causing a gasflow successively through first said ionizing chamber and then said precipitating chamber, said ionizing chamber comprising one or more insulatedly supported fine wires spaced between substantially uninsulated large electrodes; said precipitating chamber comprising oppositely charged, spaced precipitating electrodes substantially parallel to the direction of gas-flow; a stepup transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-.voltage primary winding disposed on the primary portion of the magnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages both to said ionizing wire or wires and to said precipltating electrodes; said ionizing wire or wires being of less than 32 mils diameter and being of such fineness that substantially utilizable ionization of suspended particles in the gas is obtained at a low ionizing current with a wirecharging voltage below the critical corona voltage, the unidirectlonal wire-charging voltage being below said critical corona voltage; and means energized from said tertiary winding for obtaining a predetermined response or responses to voltage-decreases enduring for longer than a predetermined time such that there will not be a response to momentary flashes in the apparatus.

'7. In combination, limited-energy, voltageconversion, relatively high-voltage-means comprising a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a lowvoltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit, and means associated with said secondary winding for energizing one or more low-current, highvoltage load-circuits; and an under voltage relay and an overvoltage relay both energized from said tertiary winding, said relays making a predetermined response or responses to an abnormal drop in voltage and an abnormal increase in volt age, respectively, and circuit-means responsive to a response of either of said relays.

8. In combination, a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magneticleakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages to one or more loadcircuits; and an undervoltage relay and an overvoltage relay both energized from said tertiary winding, said relays making a predetermined response or responses to an abnormal drop in volt-,

and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit, and means associated with said secondary winding for energizing one or more low-current, highvoltage load-circuits; and means energized from said tertiary winding for obtaining a predeteru mined response or responses both when the voltage increases and when the voltage decreases with respect to a predetermined range.

10. In combination, a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magneticleakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages to one or more load-circuits; and means energized from said tertiary winding for obtaining a predetermined response or responses both when the voltage increases and when the voltage decreases with respect to a predetermined range.

11. In combination, limited-energy, voltageconversion, relatively high-voltage means comprising a step-up transformer having a magnetizable circuit including a primary portion, a secondary portion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a lowvoltage tertiary winding both disposed on the secondary portion of the magnetizable circuit,

and a low-voltage primary winding disposed on the primary portion of the magnetizable circuit, and means associated with said secondary winding for energizing one or more low-current, highvoltage load-circuits; and means energized from said tertiary winding for obtaining a predetermined response or responses to voltage-decreases enduring for longer than a predetermined time such that there will not be a response to momentary flashes in the apparatus.

12. In combination, a step-up transformer having a magnetizable circuit including a pri mary portion, a secondary portion, and a magnetic-leakage path therebetween, said step-up transformer having a high-voltage secondary winding and a low-voltage tertiary winding both disposed on the secondary portion of the magnetizable circuit, and a low-voltage primary winding disposed on the primary portion of the megnetizable circuit; rectifying means associated with said secondary winding for supplying a unidirectional voltage or voltages to one or more load-circuits; and means energized from said tertiary winding for obtaining a predetermined response or responses to voltage-decreases enduring for longer than a predetermined time such that there will not be a response to momentary flashes in the apparatus.

RALPH L. HILDEBRAND. 

